Question

我还是新手。但是，我在mt数据库中插入数据时遇到问题。我认为我的剧本中出现了很多错误

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class Student extends JFrame
{
//Component's name
private JLabel lblName,lblAge,lblGrade;
private JTextField txtName, txtAge,txtGrade;
private JButton btnAdd;
String c;
String d;
String e;

public void Student()
    {

        Connection conn = null;
        String url = "jdbc:mysql://localhost:3306/";
        String dbName = "Information";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root";
        String password = "abcd";

    Container container = getContentPane();
    container.setLayout(new FlowLayout());

    lblName=new JLabel("Name: ");
    container.add(lblName);

    txtName=new JTextField(30);
    container.add(txtName);

    lblAge=new JLabel("Age: ");
    container.add(lblAge);

    txtAge=new JTextField(2);
    container.add(txtAge);

    lblGrade=new JLabel("Grade: ");
    container.add(lblGrade);

    txtGrade=new JTextField(1);
    container.add(txtGrade);

    btnAdd=new JButton("Add");
    container.add(btnAdd);

    btnAdd.addActionListener(new ActionListener()
        {
            public void actionPerformed(ActionEvent ev)
            {
                c=txtName.getText();
                d=txtAge.getText();
                e=txtGrade.getText();
            try
            {
                Class.forName(driver).newInstance();
                conn = DriverManager.getConnection(url + dbName, userName, password);

                PreparedStatement statement = conn.prepareStatement("INSERT INTO Information ('StudentName', 'StudentAge','Grade') VALUES ('"+c+"', '"+d+"', '"+e+"'')");
                statement.executeQuery();

            }
                catch (Exception ex)
            {
                ex.printStackTrace();
            }
            }

        });

    setSize(300,300);
    setVisible(true);

}
public static void main(String[]args)
{
    Student application = new Student();
    application.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}

}

那么，任何人都可以帮我解决这里的错误吗？请参阅下面的屏幕截图了解输出。

enter image description here

Answer 1

1 - 您不需要''使用列'StudentName'的名称，如果需要，请使用``代替''

2 - 您的查询存在问题：

...('"+c+"', '"+d+"', '"+e+"'')

你最后设置了两个''，这就产生了问题。

你为什么不用？像这样：

PreparedStatement statement = 
conn.prepareStatement("INSERT INTO Information (StudentName, StudentAge, Grade) VALUES (?, ?, ?)");

statement.setString(1, c);
statement.setString(2, d);
statement.setString(3, e);

statement.executeQuery();

您可以在此处了解有关Prepared Statement doc

的更多信息

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1 个答案: